Device for controlling the idling operation of an internal combustion engine

Abstract

A device for controlling idling operation of an internal combustion engine comprising an actuator operatively connected to a throttle valve for controlling the opening degree of the throttle valve during engine idling operation, an actuator position sensor for sensing an operating position of the actuator, a first control unit adapted to receive output signals from an engine RPM sensor, a water temperature sensor which senses the temperature of engine cooling water and the actuator position sensor to control the operation of the actuator such that the opening degree of the throttle valve is adjusted to an appropriate level to maintain the RPMs of the engine during idling at a predetermined value corresponding to the sensed temperature of the cooling water, and a second control unit independently operated from said first control unit to control the operation of the actuator in accordance with the operating position of the actuator and the temperature of the cooling water so as to limit the operating position of the actuator and thereby limit the RPMs of the engine to the predetermined value corresponding to the sensed temperature of the cooling water notwithstanding a higher value of RPMs being called for by the first control unit. As a result, abnormal increases in RPMs during the idling operation of the engine are prevented even when the first control unit malfunctions.

What is claimed is: 
     
       1. A device for controlling idling operation of an internal combustion engine comprising: an engine RPM sensor which senses rotational speed in RPMs of an engine and generates an output signal representative thereof;   a water temperature sensor which senses temperature of cooling water for the engine and generates an output signal representative thereof;   a throttle valve in an intake passage of the engine which controls flow rate of intake air sucked into the engine;   an actuator means operatively connected to said throttle valve for controlling the opening degree of said throttle valve during the idling operation of the engine;   an actuator position sensor which senses an operating position of said actuator means and generates an output signal representative thereof;   a first control means connected to receive output signals from said engine RPM sensor, said water temperature sensor, and said actuator position sensor and calling for operation of said actuator means such that the opening degree of said throttle valve is adjusted to maintain the RPMs of the engine during idling at a predetermined value corresponding to the sensed temperature of the cooling water; and   a second control means operable independently of said first control means to control the operation of said actuator means in accordance with the operating position of said actuator means and the temperature of the cooling water so as to limit the operating position of said actuator means and thereby limit the RPMs of the engine to the predetermined value corresponding to the sensed temperature of the cooling water notwithstanding a higher value of RPMs being called for by said first control means.   
     
     
       2. A device for controlling idling operation of an internal combustion engine comprising: an engine RPM sensor which senses rotational speed in RPMs of an engine and generates an output signal representative thereof;   a water temperature sensor which senses temperature of cooling water for the engine and generates an output signal representative thereof;   a throttle valve in an intake passage of the engine which controls flow rate of intake air sucked into the engine;   an actuator means operatively connected to said throttle valve for controlling the opening degree of said throttle valve during the idling operation of the engine;   an actuator position sensor which senses an operating position of said actuator means and generates an output signal representative thereof;   a control means connected to receive output signals from said engine RPM sensor, said water temperature sensor, and said actuator position sensor and calling for operation of said actuator means such that the opening degree of said throttle valve is adjusted to maintain the RPMs of the engine during idling at a predetermined value corresponding to the sensed temperature of the cooling water;   a position-limiting means connected to receive output signals from said water temperature sensor and said actuator position sensor to generate a first limit signal to said control means when the operating position of said actuator position sensor exceeds a first predetermined value and a second limit signal when the operating position of said actuator position sensor exceeds a second predetermine value; and   an actuator-limiting means operatively connected to said position-limiting means for generating a first control signal to stop the operation of said actuator means in a forward, increased-speed direction on the basis of said first limit signal and for generating a second control signal to stop the operation of said actuator means in a backward, decreased-speed direction on the basis of said second limit signal.   
     
     
       3. A device for controlling idling operation of an internal combustion engine according to claim 1 wherein said second control means includes: a position-limiting means connected to receive output signals from said water temperature sensor and said actuator position sensor to generate a limit signal to said first control means when the operating position of said actuator position sensor exceeds a predetermined value; and   an actuator-stopping means operatively connected to said position-limiting means for generating a control signal to stop the operation of said actuator means on the basis of said limit signal.